Best way to deadhead zinnias based on botany
I like to grow zinnias and sometimes to breed them. However, for just ornamental uses, I realize that deadheading them is absolutely necessary in order to keep the plants growing and branching and healthy and re-blooming.
My question is, based on sound botanical principles, what is the best way to deadhead a zinnia? In other words, how far down on the stem should you go to make the cut? If you go all the way down to a primary junction where side branches occur, you remove a lot of perfectly healthy leaves. Which might or might not be a good thing to do.
If the leaves on this stem could and would send their photosynthesized sugars over to nourish other "competing" stems, then leaving a bunch of those leaves could be a good idea. But if those sugars only go "up stem" to nourish the flower you are just now removing, then there would be no advantage to the zinnia plant to retain those leaves because they would just compete for sun and root support with leaves on other stems that haven't flowered yet.
I want to better understand how a zinnia plant "works." When removing a fading flower in the deadheading process, how much pruning of the zinnia plant is beneficial? If you see a bud, you should probably retain it because it can grow out to produce another bloom. If I knew in detail how a zinnia plant works, I would know whether the leaves above or upstem from a bud support and nourish that bud or whether they actually compete with it.
I know that rose growers have a good understanding of how to combine deadheading and pruning in a way that is beneficial to the development of the rose bush. I am seeking similar enlightenment and comprehension with regard to zinnia culture.
This summer I have used several zinnia deadheading strategies. One strategy is to remove the stem all the way back to the first side branches, leaving a little stem above the junction for "die back". This strategy removes a maximum amount of zinnia leaves along with the bloom, and tends to "open up" the plant to sun and air circulation.
A less severe strategy is to remove the stem and two or three leaves along with it, but leaving some of the lower leaves on the stem in case a lateral stem might develop at the base of some of those leaves. (In many cases, if not all cases, those future laterals never appear.)
The least severe strategy is to remove just the flowerhead down to the first leaf below it, and retain all leaves on the branch of that flowerhead. That tends to look tacky because the points of surgery tend to remain visible.
But, on the assumption that botany "knows" how a zinnia plant works, how does botany suggest that deadheading and associated pruning on a zinnia plant should be done?